Rangers manager Alex McLeish branded his side's defending "a joke" as last year's Treble winners slumped to their fourth Old Firm defeat of the season.

Goals from Henrik Larsson and Alan Thompson were enough to secure victory for Bank of Scotland Premier League champions-elect Celtic at Ibrox, with substitute Steven Thompson heading the home side a consolation.

Larsson had nodded in the opener from a free-kick in the 20th minute having lost marker Gavin Rae, while Alan Thompson's goal had been the result of an error by Zura Khizanishvili, who had been caught in possession on the edge of the box by the Swede.

McLeish said: "The goals were a joke. The first one, Henrik is a great technician and has scored with so many headers, but he got an absolute free header.

"The second was casual and slack. I said at half time Celtic were playing on our mistakes.

"Row Z was also mentioned at half time, but Zura has tried to play his way out of trouble."

The second goal had been a huge blow to Rangers and a spell followed when their goal was under intense pressure from a Hoops side which had defied Barcelona in midweek.

McLeish acknowledged that, but argued that overall there had been little in it, with Celtic's teenage goalkeeper David Marshall making two good saves in quick succession and Peter Lovenkrands squandering a chance before the break.

He said: "I think there was a five-minute spell in the second half where we looked as if we could lose a goal at any time.

"Celtic had a couple of chances, but I think overall it was a decent performance.

"The first free-kick we conceded led to the goal and it has been that story against Celtic for the past three years.

"We didn't have the breaks in front of goal. There were a couple of good saves from the young goalkeeper in the first half and Peter has missed what you would have assumed was a snip for a left-footer in that position."

Rangers forced plenty of corners and fired in more shots than the visitors, although Stanislav Varga hit the bar and Stefan Klos pulled off a superb save to deny Larsson during that five-minute spell which had alarmed McLeish.

Another Old Firm victory for Celtic put them 19 points clear of Rangers at the top of the SPL - and within two wins of regaining the championship.

"We're in a fantastic position no doubt about it," said Celtic manager Martin O'Neill.

"If we couldn't win, we had to make sure we didn't get beaten so we did wonderfully well today.

"I was delighted to be two up and after that Rangers came back into the game.

"After the second it could have gone to three or four, but they had a good save by (Stefan) Klos and we looked reasonably confident.

"But I always knew tiredness would set in and it was a nervy last 10 minutes. They are a very fine side and perform consistently well and get themselves up for the matches.

"It was almost inevitable tiredness would set in but there is nothing wrong with the spirit. They have a great desire to keep going and can play as well."